Men Yusen, Hirayama Shoshiro, Ao Shinpei, Sakurai Yasuyuki, Shibata Yuri, Lo Megan, Sato Yusuke, Murata Shigeo
Laboratory of Protein Metabolism, Graduate School of Pharmaceutical Sciences, The University of Tokyo , Tokyo, Japan.
Department of Chemistry and Biotechnology and Center for Research on Green Sustainable Chemistry, Graduate School of Engineering, Tottori University, Tottori, Japan.
J Cell Biol. 2025 Jun 2;224(6). doi: 10.1083/jcb.202406120. Epub 2025 Apr 8.
Protein aggregates are degraded by both the autophagy-lysosomal and the ubiquitin-proteasome pathways. Macroautophagy and microautophagy, two forms of the autophagy-lysosomal pathway, are widely conserved across eukaryotes. While macroautophagy has been extensively studied in the context of degradation of protein aggregates, microautophagy remains less explored. Here, we identify the UBAP1-containing ESCRT-I complex and PTPN23 as new regulators for degradation of aggregated proteins through an unbiased genome-wide CRISPR knockout screen, using a cell line expressing tau repeat domain (tauRD) aggregates. ESCRT-I recognizes ubiquitylated tauRD via the UEV domain of TSG101. The accessory protein PTPN23, instead of ESCRT-II, bridges ESCRT-I and ESCRT-III to complete the endosomal microautophagy of ubiquitylated tauRD aggregates. Our results uncover the molecular mechanism underlying the degradation of tau aggregates by endosomal microautophagy.
蛋白质聚集体可通过自噬-溶酶体途径和泛素-蛋白酶体途径进行降解。巨自噬和微自噬是自噬-溶酶体途径的两种形式，在真核生物中广泛存在。虽然巨自噬在蛋白质聚集体降解方面已得到广泛研究，但微自噬的研究仍较少。在此，我们通过无偏向全基因组CRISPR敲除筛选，利用表达tau重复结构域（tauRD）聚集体的细胞系，鉴定出含UBAP1的ESCRT-I复合物和PTPN23是聚集蛋白降解的新调节因子。ESCRT-I通过TSG101的UEV结构域识别泛素化的tauRD。辅助蛋白PTPN23而非ESCRT-II，连接ESCRT-I和ESCRT-III以完成泛素化tauRD聚集体的内体微自噬。我们的结果揭示了内体微自噬降解tau聚集体的分子机制。
